Glutathione is a substance frequently utilized for pharmaceutical agents and health foods since it has various physiological activities. The substance itself is generally an odorless powder. However, an unpleasant odor like sulfur may be developed due to the influence of heat, oxygen, light and the like during preservation in the form of a powder or a preparation containing glutathione as a main component, i.e., a glutathione preparation. In some cases, glutathione content in the preparation is lowered; consequently, the quality of glutathione is deteriorated.
As a method of suppressing deterioration of the quality of glutathione during preservation, i.e., a method of improving the preservation stability of glutathione, a method including coating the surface of the particles of a glutathione powder (see patent documents 1 and 2), a method including adding cyclodextrin (see patent documents 3 and 4) and the like are known.
However, these methods are problematic in that the operation is complicated and a sufficient effect cannot be obtained.
In view thereof, the development of a glutathione preparation that resists quality deterioration and a preservation method of glutathione that resists quality deterioration has been desired.    patent document 1: JP-A-5-176739    patent document 2: JP-A-2002-97153    patent document 3: JP-A-64-63342    patent document 4: JP-A-6-78713